Contact finger for switches



Sept. 23, 1941. E. s. CORNELL ETAL 2,256,734

CONTACT ,FINGER FR SWITCHES Filed May l2, 1958 2 Sheets-Sheet l Timunlllllllll H IIIHHIIII man 1 w1 J @www hb ,J @MIZ O/ZOU @f2 JCM. #000 iSept- 23, 1941- E. s. CORNELL ET AL 2,256,734

CONTACT FINGER FOR SWITCHES Filed May l2, 1938 2 Sheets-Sheet 2 fg?. af?.

y UHNNMU' Patented Sept. 23, 1941` CONTACT FINGER FOR SWITCHES Elias S.Cornell, Evanston, Stanley C. Killian, Oak Park, and Joseph A. Stoos,Naperville, Ill., assignors to The DeltaeStar Electric Company, Chicago,Ill., a corporation of Illinois Application May 12, 1938, Serial No.207,494

(Cl. Zim-166) 6 Claims.

This invention relates generally to velectrical switches, and moreparticularly to switches adapted to carry heavy currents.

The object and general nature of this invention is the provision of acontact structure for use in switches and the like in which the surfacesin contact are in the nature of a line 4or point, or a series of them.

A further feature of this invention is the provision of a contactstructure, utilizing the high pressure contact principle, which is builtup of the number of units or sections that are required to providesuiioient contact for the desired ampere rating.

Another feature of this invention is the provision of a contactstructure in which the desired current carrying capacity is providedwithout the use of mechanical movements, adjusting screws or the likewhich usually cause such excessive pressures that some form of auxiliaryblade motion is required to release the pressure before the switch bladecan be opened.

It is a still further object of this invention to provide a contactstructure having prestressed point or line contact elements ofsuilicient number and with sufficient pressure to carry the requiredcurrent but with low frictional resistance, thereby reducing the forcerequired to open and close the switch blade.

A further feature of this invention is the provision of a switch contactstructure in which point or line contact under pressure not onlyprovides ample contact surface for carrying current, but also provides aswitch which is kept clean by the action of the contacting points orlines in removing or scraping away the oxides and other material thattend to prevent intimate engagement. Also, in a switch of thisconstruction, due to small contact area, there is less opportunity forthe blade and contacts to freeze under ice or` sleet conditions.

A further virtue of the present Contact structure is its ability toprovide good contact which is substantially uniform even though there islack of accurate alignment of the blade and the contact structure.

A further feature of this invention is the provision of a switch havingtwo pre-stressed point or line contact elements held either together orin blade receiving position under a predetermined Figure 2 is a sideview of the construction shown in Figure 1;

Figure 3 is a View taken along the line 3-3 of Figure 1;

Figure 4 is a plan view of a modied form of the present invention;

Figure 5 is a side view of the form of the invention shown in Figure 4;and

Figures 6 to 11, inclusive, are fragmentary views showing differentforms of raised switch blade engaging portions on the inturned ends ofthe U-shaped conductor.

High pressure contacts for power switches are known. According to thetheory of high pressure contacts for power switches, a limited area ofactual engagement is put under high unit pressure. It has been foundthat such structures are capable of carrying large currents withoutundue heating. The present invention provides a high pressure switchcontact structure for use in power switches, and is designed to securetwo desirable effects. First, means is provided for insuring a very highunit pressure over a limited area, and, second, the structure of thepresent contact is such that this high pressure will be secured even ifthe parts are not accurately aligned. One of the great diculties inswitch structure is to secure accurate and permanent alignment of theblade and contact jaws. The present structure is able to provide thenecessary high unit pressure, and to do so without requiring accuratealignment of the jaw and blade. Inaccuracy of alignment does notsubstantially alter either the unit pressure secured or the area ofengagement.

According to our invention, the contact jaws of each contact unit areprovided with opposed protuberances which present approximately point orshort line contact with an interposed blade. By making theseprotuberances convex in two dimensions at right angles to each other,the desirable feature of high unit pressure and substantially uniformarea of engagement is attained, even though the blade swings in a planewhich does not coincide with the median plane of the contact jaws. Weterm this form of contact projection or protuberance which is convex inany cross section, as double convex. That is to say, the protuberancedisplays convexity in two dimensions at right angles to each other.Hence, we designate the same in the following claims as double convex toinclude not only the spherical convex form, but such variationstherefrom which permit this feature of securing good and substantiallyuniform contact even in the absence of accurate alignment of the bladeand jaws.

We are aware that power switches have been proposed wherein a convexridge extends transversely across the jaws, but lack of alignment of theblade immediately destroys the intended area or the like.

i into the stationary .contact structure. lber 35 includes a connectingsection 3l which eX- tends from the attaching portion 34 to the lower ofengagement of such switches, and We do not claim such as coming withinour invention.

Referring now more particularly to Figures 1, 2, and 3, the referencenumeral l indicates the upper end of one of the insulator stacks which.

carry the switch. `A supporting bracket 2 is bolted, as at 3, to theinsulatorl and includes a conductor receiving lug 5 and an upstandingportion 6. The blade of the switch is indicated at I il, and may be ofany usual construction,k and, as illustrated, comprises a bar of copperor similar material having its end rounded, as at;

Il, and is adapted to be swung or forced into a` closed circuit positionwith respect to a stationary contact structure.

The contact structure receiving the switchv blade Hl is indicatedin itsentirety byY the reference numeralV !5,'and includes a plurality ofgenerally U-shaped conductors iE, formed 4of copper As best shown inFigurel 1, each of the conductors It includes an intermediate or basesection l1, side portions I8 and I9, and end sections and 2l which areturned inwardly `or rearwardly alongside the' portions I8 and i9. The

ends 20 and 2| extend toward the base portieriY lTa substantialdistance, and are formed 'with raised sections 22 in the form of lugs,or proi jections which are adapted to be forced into high pressureengagement with the blade Iii when ,the

latter is moved into 'the stationary contact struc-I ture l 5; Y

`outer surfaces of the inturned conductor ends` v 20 and 2l at pointsvdirectly in line with the -pro-` i `jections 22. Y

Theseveral conductors and springs are fastened to the bracket -2 bymeans of bolts 32 which extend through the upstanding portion B of thebracket 2 and through openings in the intermediate portions I! and 25 ofthe conductors and springs, and into tapped openings 33 Vwhich areformed in the attaching portion 34 of a member 35, the outer Vend 35 ofwhich is formed to serve as a'guide to facilitate movement of the bladelil part of the guide 35, and the latter is formed with upstandingsections 38 and 39 which are flared forwardly, as at 4l, and upwardlyand outwardly, as at 42. Thus, whether the blade i5 moves directlyinwardly or inwardly from an upward direction, the guide 35 aids theblade lil in moving into the desired position. As many conductors I6 andsprings 25 may be provided as desired, depending upon the desiredcurrent carrying'capacity of the unit. This is an important feature ofthis invention in that it makes it posn sible to bulid up any desiredsize of unit.

In operation, when the blade I0 is forced into 'Y closed circuitposition between the contact sec- Vtions 20 and 2l, the springs 28 and29 force the projections V22 into high pressure engagement with ftheswitch blade. By virtue of the relatively small area of engagement atthese points and relatively large pressure exerted by the springs 25,the portions 22 wipe or scrape all oxide and 'into the contactstructure.

other material from the blade i5 so that there is actual metal-to-metalcontact under relatively high pressure, thereby providing ample contactsurface for carrying the current. Since the area of actual contact atthe points 22 is relatively small, there is materially less frictionalresistance to the movement of the blade i5 than in conventional switchesin which the contact elements have relatively large areas of contactwithV the switch blade. of contact are present, even with high pressure,there is not the scraping or cleaning action that is secured in thepresent construction.

When the switch blade lil is disengaged from the contact structure, theportions 25 and 2l are moved into engagement with oneanother bythespring arms 28 and 29,- so that when the switch `blade is open, there isless tendency for corrosion and accumulation of dirt.

Figures 4 and 5 show a modified forni of the present invention in whichtheguide 35 of Figures 1 and 2 has Vbeen'omitted. Referring now -toFigures 4 and 5, the contact structure comprises one or more flexibleconductors 55, earch of which is generally U-shapedv and has ends 5i and52 turned backwardly or inwardly toward the intermediate or base portion53 of the conductor. Y A pair of springs 55, formed of steel or the likeand also Uf-shaped, have their base sections55 disposed against theportion 53 of the `conductor 5l! and have ends 58 and 59 which bearagainst the ends 5l and 52 of the conductor. v

The ends 5l and 52 are formed with vprotuberances Si), and the springs55 Vare made so that they act against the ends 5i and 52 to hold theVprojections til against each other with a predetermined force. It willbe noted from Figure 4 that the bent portions of the conductor 5i]adjacent the ends 5l and 52 are formed in the general shape of a V so asto serve as a guide for a switch blade I9 which is adapted tombe forcedby the switch mechanism (not shown) longitudinally Theinward movement ofthe switch blade iii acts against the projections 55 to secure a wipinghigh pressure en-I gagement between the contactstructure and the bladel5. As many units may be employed as desired, and each pair of springs55 and the associated conductor 50 are secured to the bracket 6 bysuitable bolt means 52. The number of units employed will depend uponthe current carrying capacity that it is desired the contact structureshall have.

The pressure increasing projections or lugs 22 of Figure 1, and 60 ofFigure 4, are shown in these figures as protuberances formed by pressinga suitable tool vagainst the conductor ends so as to force some of thematerial of the conductor outwardly to form the protuberances. FiguresGrand 7 show the details of the construction as utilized in Figure 4. Itwill be noted that the spring ends 55 act against the conductor 50 inexact alignment with the protuberances 65.

In Figures 1, 4, 6, and Y"i, the protuberances are shown as beinggenerally spherical, thereby providing more or less point contactbetween the contact structure and the associated switch blade. If it isdesired to have more extended contact, the construction shown in Figures8 and 9 may be employed in which the conductor 55a has an elongatedprotuberance a formed therein in any suitable manner. Another way offorming generally spherical protuberances is indicated in Figuros v10and 11 in which the conductor 50h is shown as having upset portions 69o.The ad- Where such relatively large areas Vantage of this constructionis that there is more material at the protuberances than in thepreviously described structures.

It is to be observed that the protuberances 22, 22 in Figure l or Bi),6i) swing angularly when they are separated by thrusting the blade Ibetween them. This is the case because the bottom of the U-shaped bodyIB of Figure l, or 50 of Figure 4, and of the spring 25 or 55 is in eachcase rigidly clamped to the support. Hence these protuberances swingangularly away from and toward each other as they are moved by theentrance or exit of the switch blade between them. This angular motionwould be intolerable if surface contact as of two fiat surfaces againsteach other were desired. Because these protuberances are convex, theslight degree of angular motion which would destroy fiat surface contactis unobjectionable in this construction, as the change in angularposition merely presents a different point of contact withoutsubstantially altering the nature of the contact. Because of the greaterlength of metal involved in the recurved form of the contact i6, thechange in spring loading due to shift in position is less pronounced.The action is smooth and easy.

So far as we are aware, the use of point or line engagement in switchcontacts of this type is new, and therefore, while we have shown anddescribed above the preferred means in which the principles of thepresent invention have been embodied, it is to be understood that ourinvention is not to be limited to the particular details shown anddescribed, but that, in fact, widely different means may be employed inthe practice of the broader aspects of our invention.

What we claim, therefore, and desire to secure by Letters Patent is:

1. A switch member comprising a supporting member, a pair ofapproximately parallel conducting plates adapted to receive a switchblade between them, said plates being mounted upon said support forlimited motion toward and away from each other, said plates having ontheir facing surfaces double convex protuberances registering with eachother, converging spring arms bearing at their outer ends upon the backsof said plates and holding said protuberances in contact with each otherwith an initial predetermined pressure.

2. The combination of claim 1 characterized by said plates comprisingoutwardly diverging portions for guiding the switch blade between saidprotuberances, and said protuberances comprising convex surfaces ofsmall radius to produce unit pressures of high intensity.

3. The combination of claim 1 characterized by the plates constitutingintegral parts of the legs of a generally U-shaped bar of conductingmetal, the protuberance having approximately spherical surfaces, and theconverging spring arms forming two sides of a continuous fiat bar bentinto triangular form, the two arms converging at substantially a commonapex and engaging the said plates substantially at the backs of saidprotuberances.

4. An electric switch member comprising, in combination, conductingsupport means, a generally U-shaped contact member formed of fiat stripconducting material and mounted on said support means and having itsends turned inwardly for receiving a switch blade therebetween, opposingportions of said inturned ends having double convex protuberances whichproject toward each other to provide substantially point contactengagement with opposite sides of said switch blade, and a generallyU-shaped spring member nested within said U-shaped contact member withits ends bearing against said inturned ends substantially in alignmentwith the contact areas of said protuberances and biasing the same intohigh pressure contact engagement with said switch blade, said springmember being prestressed to cause mutual engagement of said contactareas under pressure when said switch blade is withdrawn from engagementtherewith.

5. An electric switch member comprising, in combination, conductingsupport means, a generally U-shaped contact member formed of iiat stripconducting material and mounted on said support means and having itsends turned inwardly for receiving a switch blade therebetween, saidinturned ends having outwardly flaring portions for guiding said switchblade into switch closed position, opposing portions of said inturnedends bearing double convex protuberances which project toward each otherto provide substantially point contact engagement with opposite sides ofsaid switch blade, and a generally U-shaped spring member of flat springstock nested within said U-shaped contact member with convergent sidesterminating in ends bearing against said inturned ends substantially inalignment with the contact areas of said deformed portions and biasingthe same into high pressure contact engagement with said switch blade.

6. An electric switch contact comprising in combination conductingsupport means provided with va substantially flat clamping face, a conftact element of flat bar stock comprising a flat base portion, integralarm portions substantially normal to said base portion, free endportions disposed in substantially parallel relation to each other andto said arm portions with the free ends extending toward the baseportion, integral guide portions intermediate the end portions and thearm portions for guiding a blade between the free end portions, saidfree end portions having double convex protuberances adapted to engageeach other when the blade is withdrawn from between them, and aprestressing spring of approximately triangular shape disposed insidesaid Contact element and having a base portion overlying and bearingagainst the flat base portion of the contact element, and a pair ofconvergent spring arms the ends of which bear against the 'backs of theend portions of the Contact element substantially in registry with theprotuberances, said spring holding said protuberances in contact under apredetermined initial pressure, whereby forcing of a blade between theprotuberances causes separation of the spring arms and a substantialincrease in the tension of said spring arms, and means for clamping thebases of the spring and the contact element together upon said clampingfaces.

ELIAS S. CORNELL. STANLEY C. KILLIAN. JOSEPH A. STOOS.

